There is a very nice RV park at the Nevada/California line on I-15. The name is Primm Valley RV Resort 702-382-1212. From Las Vegas take the number 1 exit and turn left under the freeway, 200 yards on your right.
It will be exhaust manifold hot during the summer in this area. Last year in July I crossed the area at 2:00 AM to beat the heat, balmy 107, rose to 119 in the daytime.
Good cell service in the area. We dry camp in the casino lot sometimes.